Martin Balsam did not receive an Oscar nomination, although he did receive a BAFTA nomination for portraying Harold Longman "Mr. Green" in The Taking of Pelham One, Two, Three.
Balsam performance certainly is not the focus of the film, and really the role of Green could have been forgotten in the light of the main villain Mr. Blue. Balsam though very important does make the most in humanizing one of the hijackers very well. Balsam does not try to make Mr. Green overly sympathetic in any way in regards to any sort of pleading with the audience, Mr. Green still is doing it for the money, but the humanity of Green created by Balsam especially when compared to the others is subtly but powerfully handled by Balsam.
Balsam's performance is made up of quite a few reactionary moments that are extremely well played by him. They are mostly in when Green sees the full extent of Mr. Blue's plan, and that his threats are entirely true. Balsam makes everyone of them impact well as he shows that Green really is in it far deeper than he ever wanted to be, and he portrays an honest realistic disbelief in who is essentially just an average joe who happened to come in on a job that really is not in his line in any way. Balsam is quite moving in just these small important moments best out of anyone portraying the severity of the situation.
My favorite human moments though come in his short little conversations with Mr. Blue as they wait for money. He and Shaw are great together in the way they play off the extreme contrasts in terms of the personality, but in at the same time there is a certain camaraderie and respect between the two as two men working on a project. The two have some nice humorous moments particularly when Balsam talks about Green's reason for firing which was a crime he did not commit. The two back and forth in the moment is terrific showing a human side to both character but not at all compromising the intensity of the later scenes in the film.
Balsam gives a very good performance by making Green likable, and he even effectively twists the audiences sympathy just to the right making it so you do not want the hijackers simply all to be killed. He turns Mr. Green into any actual normal man who embarks on a rather foolish endeavor. Balsam allows us to follow Mr. Green through this decision all the way through both the lows, and the seeming highs. He believably shows entirely genuine reactions to what Mr. Green goes through the entire film. Balsam with a character who could have been a throwaway he makes Green three dimensional, and doing so adds greatly to his film.